Parallelogram load sensing apparatus for a seat belt webbing

ABSTRACT

An apparatus ( 210 ) includes seat belt webbing ( 12 ), a parallelogram linkage ( 220 ), a sensor lever ( 370 ), and a sensor ( 379 ). The seat belt webbing ( 12 ) helps to protect the occupant ( 14 ) of the vehicle ( 18 ). The parallelogram linkage ( 220 ) includes a first beam ( 352 ) and a second beam ( 362 ) parallel to the first beam ( 352 ). The first and second beams ( 352, 362 ) each bend in response to at least part of a load applied by the seat belt webbing ( 12 ). The sensor lever ( 370 ) is interposed between the first and second beams ( 352 ). The sensor lever ( 370 ) has a connection with the first and second beams ( 352 ). The connection causes the sensor lever ( 370 ) to deflect upon bending of the first and second beams ( 352 ). The sensor ( 379 ) senses the deflection of the sensor lever ( 370 ) and provides an output signal indicative of the amount bending of the first and second beams ( 352, 362 ).

TECHNICAL FIELD

[0001] The present invention relates to an apparatus for sensing a load,and more particularly, to an apparatus for sensing a load applied byvehicle seat belt webbing.

BACKGROUND OF THE INVENTION

[0002] A conventional vehicle seat belt system restrains an occupant ofa vehicle seat. The system includes seat belt webbing anchored to thefloor pan of the vehicle, a tongue on the webbing, a seat belt bucklefor receiving the tongue, and an apparatus for sensing the tensionplaced on the seat belt webbing by the occupant. An occupant weightsensor may be associated with the vehicle seat. The weight sensorprovides an output signal that indicates a sensed weight of the occupantof the seat. An inflatable vehicle occupant protection device, such asan air bag, is inflated under the control of the weight sensor.

[0003] When the vehicle experiences a collision, a source of inflationfluid is actuated by a controller and directs inflation fluid into theinflatable vehicle occupant protection device. The controller receivesan output signal from the weight sensor and controls the amount ofinflation fluid directed into the inflatable vehicle occupant protectiondevice in response to the output signal from the weight sensor. If theweight sensed by the weight sensor is below a predetermined amount(i.e., a low weight in the seat or no occupant in the seat), then thecontroller disables the source of inflation fluid to prevent inflationof the inflatable vehicle occupant protection device. The controllerthus controls the fluid pressure in the inflatable vehicle occupantprotection device and the restraining force provided by the inflatablevehicle occupant protection device based on the sensed weight of theoccupant. The controller may also disable the inflatable vehicleoccupant protection device.

[0004] The seat belt webbing, when buckled about an occupant, may beplaced under tension. In this case, the weight sensor may not sense anaccurate weight of the occupant. The seat belt tension sensing apparatuscan produce an output signal that can be combined with the output signalfrom the weight sensor by the controller so that a more accurate weightvalue for the vehicle occupant is produced.

[0005] An apparatus that can determine the vertical component of thetension on the seat belt webbing and the angle at which that tension isapplied can be utilized by the controller to more accurately determinethe weight of the vehicle occupant. Also, such apparatus may determinethe type of object in the vehicle seat, such as a child seat.

SUMMARY OF THE INVENTION

[0006] The present invention relates to an apparatus that includes seatbelt webbing, a parallelogram linkage, a sensor lever, and a sensor. Theseat belt webbing helps to protect the occupant of the vehicle. Theparallelogram linkage includes a first beam and a second beam parallelto the first beam. The first and second beams each bend in response to aload applied by the seat belt webbing. The sensor lever is interposedbetween the first and second beams. The sensor lever has a connectionwith the first and second beams that causes the sensor lever to deflectupon bending of the first and second beams. The sensor senses thedeflection of the sensor lever and provides an output signal indicativeof the amount bending of the first and second beams and, therefore, theamount of load applied by the seat belt webbing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The foregoing and other features of the invention will becomemore apparent to one skilled in the art upon consideration of thefollowing description of the invention and the accompanying drawings, inwhich:

[0008]FIG. 1 is a schematic view of a seat belt system including anapparatus embodying the present invention;

[0009]FIG. 2 is a schematic isometric view of the apparatus of FIG. 1that is part of the seat belt system;

[0010]FIG. 3 is a schematic view of the apparatus of FIG. 2 under anunloaded condition;

[0011]FIG. 4 is a schematic view of the apparatus of FIG. 2 under aloaded condition;

[0012]FIG. 5 is a schematic view of the apparatus of FIG. 2 under adifferent loaded condition; and

[0013]FIG. 6 is a schematic view of the apparatus of FIG. 2 under astill different loaded condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention relates to a seat belt system for avehicle. As illustrative of the present invention, a seat belt system 10(FIG. 1) includes seat belt webbing 12 for restraining a vehicleoccupant 14, in a driver's seat 16 in a vehicle 18. It is to beunderstood that the present invention could also be used with a seatbelt system for restraining an object, such as a child safety seat orbooster seat, in a front or rear passenger seat of the vehicle 18. Theseat belt webbing 12 is extensible about the vehicle occupant 14. Oneend of the seat belt webbing 12 is anchored to the vehicle 18 at ananchor 20 located on one side of the vehicle seat 16. The opposite endof the seat belt webbing 12 is attached to a seat belt retractor 22 thatis typically secured to the vehicle 18 on the same side of the vehicleseat 16 as the anchor 20.

[0015] As shown in FIG. 1 intermediate its ends, the seat belt webbing12 passes through a tongue assembly 24 and a turning loop, or D-ring 26,which is located above the retractor 22 and the anchor point 20. Whenthe seat belt webbing 12 is not in use, the seat belt webbing is woundon a spool of the retractor 22. The spool is biased in a direction towind the webbing on the spool by a biasing spring, as is known. To usethe seat belt webbing 12, the tongue assembly 24 is extended across thelap and torso of the vehicle occupant 14 and connected with a buckle 30.The buckle 30 is connected to the vehicle 18 by an anchor 32 on theopposite side of the vehicle seat 16 from the anchor 20 and theretractor 22.

[0016] An inflatable vehicle occupant protection device, such as an airbag 43, is stored in an uninflated condition in a portion of the vehicle18, such as a steering wheel 40 or a dashboard 41 of the vehicle. Whenthe vehicle 18 experiences a collision in which it is desirable toinflate the air bag 43, an inflator 42 is actuated and providesinflation fluid for inflating the air bag. The inflation fluid may begenerated by combustion of pyrotechnic material, simply released from apressurized container, or provided by a hybrid inflator, all as known inthe art. The inflation fluid directed into the air bag 43 inflates theair bag from the uninflated condition to an inflated condition (notshown) in which the air bag extends into an occupant compartment 44 ofthe vehicle 18. The air bag 43 then helps to protect the vehicleoccupant 14 from a forceful impact with a part of the vehicle 18 (i.e.,the steering wheel 40, the dashboard 41, etc.).

[0017] An electronic controller 44, such as a microcomputer, isoperatively connected to a known vehicle collision sensor 45. Once thecontroller 44 determines that a collision is occurring and thatinflation of the air bag 43 is necessary to help protect the vehicleoccupant 14 in the vehicle seat 16, the controller actuates the inflator42, which is operatively connected to the controller. The amount ofinflation fluid directed into the air bag 43 is controlled so that theair bag provides a cushioning and restraining force that is related tothe weight of the vehicle occupant 14 in the vehicle seat 16.

[0018] A weight sensor 50 is mounted on or in the vehicle seat 16. Theweight sensor 50 is operatively connected to the controller 44. Theweight sensor 50 senses a weight of the vehicle occupant 14 or theobject in the vehicle seat 16. The sensed weight may differ from theactual weight of the vehicle occupant 14 under differing conditions.

[0019] During normal operation of the vehicle 18, the vehicle occupant14 usually has the tongue assembly 24 connected with the buckle 30. Atension on a lap belt portion of the seat belt webbing 12, includingtension applied by the retractor 22, acts on the vehicle occupant 14.The tension in the lap belt portion of the seat belt webbing 12 pullsdown at an angle on the vehicle occupant 14 (FIG. 1) causing the weightsensor 50 to be subjected to the weight of the vehicle occupant 14 alongwith a vertical component of downward force resulting from the tensionin the lap belt portion of the seat belt webbing 12. The output signalfrom the weight sensor 50 thus indicates a sensed weight of the vehicleoccupant 14 which may be greater than the actual weight of the vehicleoccupant.

[0020] Additionally, during a vehicle collision, the vehicle occupant 14may tend to move forward in the vehicle and produce a tension on theseat belt webbing 12. This tension in the seat belt webbing 12 may pullupward at an angle on the vehicle occupant 14 causing the weight sensor50 to be subjected to less weight than the weight sensed during normaloperation. The output signal from the weight sensor 50 thus indicates asensed weight of the vehicle occupant 14 which may be less than theactual weight of the vehicle occupant.

[0021] An apparatus 210 for sensing a seat belt tension load senses themagnitude of the tension in the seat belt webbing 12 and the directionthat the tension acts on the apparatus 210. The apparatus 210 providestwo output signals: the first signal indicating the vertical componentof the tension in the seat belt webbing 12 and the second signalindicating the direction of the tension. The output signals from theweight sensor 50 and the apparatus 210 are received by the controller44.

[0022] During normal operation, the controller 44 determines a computedweight of the vehicle occupant 14 as a function of both the sensedweight and the vertical component of tension in the seat belt webbing12. The sensed weight from the weight sensor 50 differs from the actualweight of the vehicle occupant 14 by a first amount. The computed weightdiffers from the actual weight of the vehicle occupant 14 by a secondamount that is less than the first amount and may be zero.

[0023] The controller 44 controls the amount of inflation fluid directedto the air bag 43 by the inflator 42 based on the computed weight of thevehicle occupant 14 in the vehicle seat 16. If the computed weight isbelow a predetermined value or zero (indicating the presence of a childseat in the seat or indicating the seat is not occupied), the controller44 disables the inflator 42 to prevent inflation fluid from beingdirected to the air bag 43. Alternatively, if the computed weight isbelow the predetermined value, the controller 44 may cause the inflator42 to direct a minimal amount of inflation fluid to the air bag 43.

[0024] The controller 44 may have in memory a look-up table of aplurality of empirical sensed weight values, a plurality of empiricalvertical component of seat belt tension values, and a plurality ofcomputed weight values corresponding to combining of the sensed weightvalues and the vertical component of tension values. The computed weightvalues stored in the look-up table could be predetermined empiricallyand/or through computations based on a predetermined functionalrelationship between the values of the sensed weight and the verticalcomponent of tension.

[0025] The controller 44 can then identify a predetermined computedweight value corresponding to empirical values of the sensed weight andthe vertical component of tension. Alternatively, the controller 44could determine the computed weight by performing a computation based ona predetermined functional relationship between the sensed weight andthe vertical component of tension that is derived from empirical data.One such functional relationship could be subtracting the verticalcomponent of tension from the sensed weight (during normal vehicleoperation). In either case, the computed weight determined by thecontroller 44 more closely approximates the actual weight of the vehicleoccupant 14, as compared with the sensed weight indicated by the weightsensor 50, since the effect of the vertical component of tension in theseat belt webbing 12 is considered in determining the computed weight.

[0026] The controller 44 uses the output signal indicative of thedirection of the tension in the seat belt webbing 12 to determine thesize and shape of the object in the vehicle seat 16. The direction oftension indicates whether a child safety seat or booster seat ispositioned in a front or rear passenger seat in the vehicle 18. Asupplemental sensor of known type may also be used to sense the size andshape of the object in the seat to determine if a child safety seat orbooster seat is positioned in the passenger seat.

[0027] If a child safety seat or booster seat is positioned in the seat,the tongue assembly 24 is connected with the buckle 30 to secure thechild safety seat or booster seat to the seat. Typically, the seat beltwebbing 12 is pulled as tight as possible to secure the child safetyseat or booster seat to the seat. The tension in the seat belt webbing12 pulls down on the child safety seat or booster seat causing theweight sensor 50 to be subjected to the weight of the child safety seator booster seat with the child therein and the downward force resultingfrom the vertical component of tension in the seat belt webbing. Theoutput signal from the weight sensor 50 thus indicates a sensed weightof the child safety seat or booster seat and the child therein which isgreater than the actual weight of the child safety seat or booster seatand the child.

[0028] The apparatus 210 provides output signals indicative of thevertical component of tension in the seat belt webbing 12 and thedirection of the tension. The controller 44 determines the computedweight of the child safety seat or booster seat and the child therein.If the weight sensor 50 senses that a child safety seat or booster seatis positioned in the seat, the controller 44 disables the source ofinflation fluid to prevent inflation of the air bag 43. Alternatively,if the weight sensor 50 senses that a child safety seat or booster seatis positioned in the passenger seat, the controller 44 may cause thesource of inflation fluid to direct a minimal amount of inflation fluidto the air bag 43.

[0029] The direction signal also is used to determine the presence of achild safety seat or booster seat in the seat. If the direction signalindicates that the seat belt webbing 12 is under tension at an anglerelative to vertical less than a predetermined amount, the controller 44will then determine that a child safety seat or booster seat is present.Typically such an angle is 45°.

[0030] The apparatus 210 includes a dual parallelogram linkage 220; ahousing 280 for connection to the seat belt webbing 12; and a fixtureblock 510, for attaching the apparatus to the floor pan of the vehicle18 at the anchor 20. The apparatus 210 further includes a restrictionplate 520 for preventing over-travel of the dual parallelogram linkage220; and a fastener assembly 610 for interconnecting the dualparallelogram linkage, the fixture block 510, and the restriction plate.The dual parallelogram linkage 220 includes a first parallelogramlinkage 320 and a second parallelogram linkage 420 adjacent the firstparallelogram linkage.

[0031] The first parallelogram linkage 320 defines a parallelogram in avertical plane perpendicular to the floor pan of the vehicle 18 andparallel to the forward/rearward movement of the vehicle 18. The firstparallelogram linkage 320 includes a first beam 352 and a second beam362 extending parallel to the first beam. The first and second beams352, 362 have adjacent, fixedly interconnected first ends 354, 364 thatreceive at least part of the load from the seat belt webbing 12. Thefirst and second beams 352, 362 further have adjacent, fixedlyinterconnected second ends 356, 366 opposite the respective first ends354, 364. Intermediate portions 355, 365 of the respective first andsecond beams 352, 362 interconnect the first ends 354, 364 and secondends 356, 366 of the first and second beams 352, 362, respectively. Thesecond ends 356, 366 transmit at least part of the load from the seatbelt webbing 12 to the floor pan of the vehicle 18.

[0032] The first and second beams 352, 362 are identical in constructionand bend in response to a load applied to the beams. The firstparallelogram linkage 320 further includes a first sensor lever 370interposed between the intermediate portions 355, 365 and the secondends 356, 366 of the first and second beams 352, 362.

[0033] The intermediate portions 355, 365 of the first and second beams352, 362 have smaller vertical dimensions than the ends 354, 356, 364,366 of each beam 352, 362 (as viewed in FIGS. 2-6). The intermediateportions 355, 365 are vertically thinner than the ends 354, 356, 364,366. The vertically larger ends 354, 356, 364, 366 and the intermediateportions 355, 365 of the beams 352, 362 create a closed parallelogramconfiguration (as viewed in FIGS. 2-6).

[0034] The first sensor lever 370 has a longitudinal axis 100 in anunloaded, or unstressed, condition (as viewed in FIG. 3). The first andsecond beams 352, 362 are disposed above and below, respectively, theaxis 100 of the first sensor lever 370 with the intermediate portions355, 365 of the beams located at equal distances from the axis (asviewed in FIG. 3). The first sensor lever 370 further has a first endportion 372 and a second end portion 374 opposite the first end portion.The second end portion 374 of the first sensor lever 370 is interposedbetween, and has a fixed connection with, the second ends 356, 366 ofthe first and second beams 352, 362. The second end portion 374 of thefirst sensor lever 370 has an opening (not shown) for fixing the firstsensor lever 370 in an interposed position between the second ends 356,366 of the first and second beams 352, 362.

[0035] The first end portion 372 of the first sensor lever 370 isoperatively associated with the intermediate portions 355, 365 of thefirst and second beams 352, 362. This arrangement causes the firstsensor lever 370 to bend upon vertical movement of the first ends 354,364 of the first and second beams 352, 362 (as viewed in FIGS. 4-6).

[0036] The first sensor lever 370 typically has a vertical thicknesssubstantially less than that of each intermediate portion 355, 365 suchthat the stiffness of the first sensor lever is about one-tenth that ofthe combined stiffness of each intermediate portion. For example, if aten-pound vertical load would deflect the first sensor lever 370 apredetermined amount, a one hundred pound vertical load would berequired to deflect the two intermediate portions 355, 365 that samepredetermined amount.

[0037] The first sensor lever 370 and the first and second beams 352,362 are typically constructed of a suitable spring-like material such assteel or an engineered laminate. Aluminum may also be used entirely orin combination with steel or other suitable metal.

[0038] The first parallelogram linkage 320 further includes a firstsensor 379 for sensing the bending of the first sensor lever 370 and forproviding an output signal indicative of the amount of bending of thefirst sensor lever. The amount of bending of the first sensor lever 370is directly related to the amount of bending of the first and secondbeams 352, 362. The first sensor 379 provides an output signal dependentupon the amount of bending of the first sensor lever 370. The firstsensor 379 is typically a strain gauge sensor that is applied to thefirst end portion 372 of the first sensor lever 370, preferably by asilk-screening process.

[0039] The first end portion 372 of the first sensor lever 370 may beover-molded with a polymer (not shown) for environmentally sealing thefirst sensor 379 mounted thereon. The first end portion 372 of the firstsensor lever 370 may then have a greater vertical thickness than theunsealed second end portion 374 of the first sensor lever 370.

[0040] The first end portion 372 of the first sensor lever 370 furtherincludes an upper curved surface 375 and a lower curved surface 377. Theupper curved surface 375 engages, or abuts, a lower surface 358 of theintermediate portion 355 of the first beam 352. The lower curved surface377 engages, or abuts, an upper surface 368 of the intermediate portion365 of the second beam 362. These curved surfaces 375, 377 may beportions of a sphere or some other suitably curved shape. The curvedsurfaces 375, 377 may also be curved end portions of fasteners, such asrivets, mounted on the first sensor lever 370 or on the upper and lowersurfaces 358, 368 of the intermediate portions 355, 365 of the first andsecond beams 352, 362.

[0041] The first sensor lever 370 essentially bends only in a verticalplane about a horizontal axis (as viewed in FIGS. 4-6) when the load isapplied to the apparatus 210. The lower and upper surfaces 358, 368 ofthe beams 352, 362 define spherical actuation points that will “roll”with the upper and lower curved surfaces 375, 377, respectively, if atorsional load, which tends to twist the first parallelogram linkage 320about the axis 100, for example, is placed on the first parallelogramlinkage. A lateral load on the first parallelogram linkage 320,transverse to the axis 100, is transferred through both beams 352, 362from the seat belt webbing 12 to the floor pan of the vehicle 18. Thefirst sensor lever 370, and the first sensor 379, thereby incur minimaltorsional or lateral loading due to the spherical actuation points thatallow minimal torsional deflection of the first sensor lever 370 as thefirst parallelogram linkage 320 is twisted about the axis 100.

[0042] The second parallelogram linkage 420 defines a parallelogram in avertical plane perpendicular to the floor pan of the vehicle 18 andparallel to the forward/rearward movement of the vehicle 18. The secondparallelogram linkage 420 includes a third beam 452 and a fourth beam462 extending parallel to the third beam. The third and fourth beams452, 462 have adjacent, fixedly interconnected first ends 454, 464 thatreceive part of the load from the seat belt webbing 12. The third andfourth beams 452, 462 further have adjacent, fixedly interconnectedsecond ends 456, 466 opposite the respective first ends 454, 464.Intermediate portions 455, 465 of the respective third and fourth beams452, 462 interconnect the first ends 454, 464 and second ends 456, 466of the third and fourth beams 452, 462, respectively. The second ends456, 466 transmit part of the load from the seat belt webbing 12 to thefloor pan of the vehicle 18.

[0043] The third and fourth beams 452, 462 are identical in constructionand bend in response to a load applied to the beams. The secondparallelogram linkage 420 further includes a second sensor lever 470interposed between the intermediate portions 455, 465 and the secondends 456, 466 of the third and fourth beams 452, 462.

[0044] The intermediate portions 455, 465 of the third and fourth beams452, 462 have smaller vertical dimensions than the ends 454, 456, 464,466 of each beam 452, 462 (as viewed in FIGS. 3-6). The intermediateportions 455, 465 are vertically thinner than the ends 454, 456, 464,466. The vertically larger ends 454, 456, 464, 466 and the intermediateportions 455, 465 of the beams 452, 462 create a closed parallelogramconfiguration (as viewed in FIGS. 3-6).

[0045] The second sensor lever 470 has the same longitudinal axis 100 asthe first sensor lever 370 in an unloaded, or unstressed, condition (asviewed in FIG. 3). The third and fourth beams 452, 462 are disposedabove and below, respectively, the axis 100 of the second sensor lever370 with the intermediate portions 455, 465 of the beams located atequal distances from the axis (as viewed in FIG. 3). The second sensorlever 470 further has a first end portion 472 and a second end portion474 opposite the first end portion. The second end portion 474 of thesecond sensor lever 470 is interposed between, and has a fixedconnection with, the second ends 456, 466 of the third and fourth beams452, 462. The second end portion 474 of the second sensor lever 470 hasan opening (not shown) for fixing the second sensor lever 470 in aninterposed position between the second ends 456, 466 of the third andfourth beams 452, 462.

[0046] The first end portion 472 of the second sensor lever 470 isoperatively associated with the intermediate portions 455, 465 of thethird and fourth beams 452, 462. This arrangement causes the secondsensor lever 470 to bend upon vertical movement of the first ends 454,464 of the third and fourth beams 452, 462 (as viewed in FIGS. 4-6).

[0047] The second sensor lever 470 typically has a vertical thicknesssubstantially less than that of each intermediate portion 455, 465 suchthat the stiffness of the second sensor lever is about one-tenth that ofthe combined stiffness of each intermediate portion. For example, if aten-pound vertical load would deflect the second sensor lever 470 apredetermined amount, a one hundred pound vertical load would berequired to deflect the two intermediate portions 455, 465 that samepredetermined amount.

[0048] The second sensor lever 470 and the third and fourth beams 452,462 are typically constructed of a suitable spring-like material such assteel or an engineered laminate. Aluminum may also be used entirely orin combination with steel or other suitable metal.

[0049] The second parallelogram linkage 420 further includes a secondsensor 479 for sensing the bending of the second sensor lever 470 andfor providing an output signal indicative of the amount of bending ofthe second sensor lever. The amount of bending of the second sensorlever 470 is directly related to the amount of bending of the third andfourth beams 452, 462. The second sensor 479 provides an output signaldependent upon the amount of bending of the second sensor lever 470. Thesecond sensor 479 is typically a strain gauge sensor that is applied tothe first end portion 472 of the second sensor lever 470, preferably bya silk-screening process.

[0050] The first end portion 472 of the second sensor lever 470 may beover-molded with a polymer (not shown) for environmentally sealing thesecond sensor 479 mounted thereon. The first end portion 472 of thesecond sensor lever 470 may then have a greater vertical thickness thanthe unsealed second end portion 474 of the second sensor lever 470.

[0051] The first end portion 472 of the second sensor lever 470 furtherincludes an upper curved surface 475 and a lower curved surface 477. Theupper curved surface 475 engages, or abuts, a lower surface 458 of theintermediate portion 455 of the third beam 452. The lower curved surface477 engages, or abuts, an upper surface 468 of the intermediate portion465 of the fourth beam 462. These curved surfaces 475, 477 may beportions of a sphere or some other suitably curved shape. The curvedsurfaces 475, 477 may also be curved end portions of fasteners, such asrivets, mounted on the second sensor lever 470 or on the upper and lowersurfaces 458, 468 of the intermediate portions 455, 465 of the third andfourth beams 452, 462.

[0052] The second sensor lever 470 essentially bends only in a verticalplane about a horizontal axis (as viewed in FIGS. 4-6) when the load isapplied to the apparatus 210. The lower and upper surfaces 458, 468 ofthe beams 452, 462 define spherical actuation points that will “roll”with the upper and lower curved surfaces 475, 477, respectively, if atorsional load, which tends to twist the second parallelogram linkage420 about the axis 100, for example, is placed on the secondparallelogram linkage. A lateral load on the second parallelogramlinkage 420, transverse to the axis 100, is transferred through bothbeams 452, 462 from the seat belt webbing 12 to the vehicle floor pan19. The second sensor lever 470, and the second sensor 479, therebyincur minimal torsional or lateral loading due to the sphericalactuation points that allow minimal torsional deflection of the secondsensor lever 470 as the second parallelogram linkage 420 is twistedabout the axis 100.

[0053] The housing 280 is typically constructed of a suitable metal suchas steel. The housing 280 has a first end portion 281 for fixedattachment to the first ends 354, 364 of the first and second beams 352,362 and a second end portion 282 for fixed attachment to the first ends454, 464 of the third and fourth beams 452, 462. The housing 280 isattached to the dual parallelogram linkage 220 such that no rotation canoccur about any horizontal axis unless the entire housing rotates (i.e.,no relative rotation).

[0054] The first end portion 281 of the housing 280 includes an upperhorizontal portion 283, a lower horizontal portion 285, and a verticalintermediate portion 284 interconnecting the upper and lower portions.The second end portion 282 of the housing 280 includes an upperhorizontal portion 293, a lower horizontal portion 295, and a verticalintermediate portion 294 interconnecting the upper and lower portions(as viewed in FIG. 3).

[0055] The housing further includes a vertical connection member 285interconnecting the first end portion 281 and the second end portion282. An upper part 286 of the connection member 285 has an opening 287for attaching the seat belt webbing 12 to the housing 280. The upperpart 286 directly receives the load from the seat belt webbing 12.

[0056] The fastener assembly 610 includes a fastener 620 and a washer,or fastener member 630. The fastener 620 may be a bolt with a head thatclamps the fastener member 630 against an upper surface 523 of therestriction plate 520. As viewed in FIGS. 3-6, the shaft of the fastener620 extends downward from the head through the fastener member 630, anopening in the restriction plate 520, an opening in the second ends 356,456 of the first and third beams 352, 452, an opening in the second endportions 374, 474 of the first and second sensor levers 370, 470, anopening in the second ends 366, 466 of the second and fourth beams 362,462, and into a threaded opening 511 in the fixture block 510. Thefixture block 510 is fixed to the floor pan of the vehicle 18 byfastener, weld, or other suitable method (not shown).

[0057] The fastener 620, housing 280, and restriction plate 520 may beconstructed of a suitable metal such as stainless steel. Othercorrosion-resistant materials of sufficient strength may also be used.

[0058] The first beam 352 of the first parallelogram linkage 320 and thethird beam 452 of the second parallelogram linkage 420 may beconstructed as a single piece with the second ends 356, 456 comprising amiddle portion with an opening for receiving the fastener 610 (as viewedin FIGS. 2-6). Similarly, the second beam 362 of the first parallelogramlinkage 320 and the fourth beam 462 of the second parallelogram linkage420 may be constructed as a single piece with the second ends 366, 466comprising a middle portion with an opening for receiving the fastener610 (as viewed in FIGS. 2-6). The first sensor lever 370 of the firstparallelogram linkage 320 and the second sensor lever 470 of the secondparallelogram linkage 420 also may be constructed as a single piece withthe second end portions 374, 474 comprising a middle portion forreceiving the fastener 610 (as viewed in FIGS. 2-6).

[0059] When a directly upward load (as viewed in FIG. 4) is placed onthe seat belt webbing 12 and the housing 280, the load is transmittedthrough the first ends 354, 364 of the first and second beams 352, 362and the first ends 454, 464 of the third and fourth beams 452, 462.Since the second ends 356, 366, 456, 466 of the first, second, third,and fourth beams 352, 362, 452, 462 are fixed to the floor pan of thevehicle 18 through the fixture block 510, the first ends 354, 364, 454,464 of the first, second, third, and fourth beams 352, 362, 452, 462will move upward with the housing 280. As the first ends 354, 364, 454,464 move upward, the intermediate portions 355, 365, 455, 465resiliently deflect upward (as viewed in FIG. 5).

[0060] The first, second, third, and fourth beams 352, 362, 452, 462 actas spring elements transferring the directly upward load from the seatbelt webbing 12 to the floor pan of the vehicle 18. The thinner verticaldimensions of the intermediate portions 355, 365, 455, 465 of the first,second, third, and fourth beams 352, 362, 452, 462 facilitate upwarddeflection of the first ends 354, 364, 454, 464 of the beams while thesecond ends 356, 366, 456, 466 remain vertically fixed relative to thefloor pan of the vehicle 18.

[0061] Because of the fixed attachment of the housing 280 to the firstends 354, 364, 454, 464 of the first, second, third, and fourth beams352, 362, 452, 462, the housing is constrained to move mainly vertically(linearly upward) when directly upward force is applied to the housing.The housing 280 is constrained horizontally. The vertically deflectedintermediate portions 355, 365, 455, 465 of the beams 352, 362, 452, 462thereby assume “S” shapes (as viewed in FIG. 4).

[0062] When the controller 44 receives the signals from the first sensor379 and the second sensor 479, the controller compares the signals anddetermines the direction (or angle) of the load by analyzing thedifference (if any) between the magnitude of the signals. The controller44 also determines the magnitude of the vertical component of the loadby analyzing the signals. Adding the output from the two signals is onepossible method for determining this magnitude.

[0063] When an upward and to the right load (as viewed in FIG. 5) isplaced on the seat belt webbing 12 and the housing 280, the load istransmitted through the first ends 354, 364 of the first and secondbeams 352, 362 and the first ends 454, 464 of the third and fourth beams452, 462. Since the second ends 356, 366, 456, 466 of the first, second,third, and fourth beams 352, 362, 452, 462 are fixed to the floor pan ofthe vehicle 18 through the fixture block 510, the first ends 354, 364,454, 464 of the first, second, third, and fourth beams 352, 362, 452,462 will move upward with the housing 280. As the first ends 354, 364,454, 464 move upward, the intermediate portions 355, 365, 455, 465resiliently deflect upward (as viewed in FIG. 5).

[0064] The first, second, third, and fourth beams 352, 362, 452, 462 actas spring elements transferring the upward, angled load from the seatbelt webbing 12 to the floor pan of the vehicle 18. The thinner verticaldimensions of the intermediate portions 355, 365, 455, 465 of the first,second, third, and fourth beams 352, 362, 452, 462 facilitate upwarddeflection of the first ends 354, 364, 454, 464 of the beams while thesecond ends 356, 366, 456, 466 remain vertically fixed relative to thefloor pan of the vehicle 18.

[0065] Because of the fixed attachment of the housing 280 to the firstends 354, 364, 454, 464 of the first, second, third, and fourth beams352, 362, 452, 462, the housing is constrained to move mainly vertically(linearly upward) with a slight rotation when upward angled force isapplied to the housing. The housing 280 is constrained horizontally. Thevertically deflected intermediate portions 355, 365, 455, 465 of thebeams 352, 362, 452, 462 thereby assume “S” shapes (as viewed in FIG. 5)with the first sensor lever 370 deflecting upward more than the secondsensor lever 470.

[0066] When the controller 44 receives the signals from the first sensor379 and the second sensor 479, the controller compares the signals anddetermines the direction (or angle) to the right of the load from adirectly vertical load (FIG. 4) by analyzing the difference between themagnitude of the signals. The controller 44 also determines themagnitude of the vertical component of the load by analyzing thesignals. Adding the output from the two signals is one possible methodfor determining this magnitude.

[0067] When an upward and to the left load (as viewed in FIG. 6) isplaced on the seat belt webbing 12 and the housing 280, the load istransmitted through the first ends 354, 364 of the first and secondbeams 352, 362 and the first ends 454, 464 of the third and fourth beams452, 462. Since the second ends 356, 366, 456, 466 of the first, second,third, and fourth beams 352, 362, 452, 462 are fixed to the floor pan ofthe vehicle 18 through the fixture block 510, the first ends 354, 364,454, 464 of the first, second, third, and fourth beams 352, 362, 452,462 will move upward with the housing 280. As the first ends 354, 364,454, 464 move upward, the intermediate portions 355, 365, 455, 465resiliently deflect upward (as viewed in FIG. 6).

[0068] The first, second, third, and fourth beams 352, 362, 452, 462 actas spring elements transferring the upward, angled load from the seatbelt webbing 12 to the floor pan of the vehicle 18. The thinner verticaldimensions of the intermediate portions 355, 365, 455, 465 of the first,second, third, and fourth beams 352, 362, 452, 462 facilitate upwarddeflection of the first ends 354, 364, 454, 464 of the beams while thesecond ends 356, 366, 456, 466 remain vertically fixed relative to thefloor pan of the vehicle 18.

[0069] Because of the fixed attachment of the housing 280 to the firstends 354, 364, 454, 464 of the first, second, third, and fourth beams352, 362, 452, 462, the housing is constrained to move mainly vertically(linearly upward) with a slight rotation when upward angled force isapplied to the housing. The housing 280 is constrained horizontally. Thevertically deflected intermediate portions 355, 365, 455, 465 of thebeams 352, 362, 452, 462 thereby assume “S” shapes (as viewed in FIG. 6)with the first sensor lever deflecting upward less than the secondsensor lever 470.

[0070] When the controller 44 receives the signals from the first sensor379 and the second sensor 479, the controller compares the signals anddetermines the direction (or angle) to the left of the load from adirectly vertical load (FIG. 4) by analyzing the difference between themagnitude of the signals. The controller 44 also determines themagnitude of the vertical component of the load by analyzing thesignals. Adding the output from the two signals is one possible methodfor determining this magnitude.

[0071] The dual parallelogram linkage 220 may receive cross-car forcesthat act transverse to the axis 100 of the first and second sensorlevers 370, 470. Such forces may impart torsional forces about the axis100 to the first, second, third, and fourth beams 352, 362, 452, 462, asdiscussed above. However, any rotation that is incurred by the dualparallelogram linkage 220 about the axis 100 will not significantlyaffect the spring rate, or stiffness, of the beams 352, 362, 452, 462 tovertical loading at the first ends 354, 364, 454, 464. The dual,identical beam configuration of the first and second parallelogramlinkages 320, 420, with each beam 352, 362, 452, 462 identicallyassociated with the axis 100, balances any rotation about the axiscreated by this torsional loading such that the effective moment ofinertia of the beams about the axis remains unchanged even when thebeams are under a deflected condition. For example, if torsional loadingof the beams 352, 362, 452, 462 has occurred, tension or compressionstresses induced in the first and third beams 352, 452 would be offsetby equal and opposite tension and compression stresses induced in thesecond and fourth beams 362, 462.

[0072] Further, the first and third beams 352, 462, acting in tandemwith the second and fourth beams 362, 462, balance any cross-sectionaldeformations of the beams that would alter the vertical spring rate(i.e., if only beams on one side of the axis 100 would be utilized,etc.). The torsional reaction of the dual beam configuration is thusequal about the axis 100, but opposite, and the vertical spring rateremains constant even after some deflection (and some cross-sectionaldeformation) has occurred.

[0073] The relationship, or spring rate, of the vertical load placed onthe first ends 354, 364, 454, 464 of the beams 352, 362, 452, 462 by theseat belt webbing 12 and the housing 280 to the vertical displacement ofthe first ends of the beams is linear, constantly proportional,predictable, and consistent for differing amounts of upward travel ofthe first ends. Thus the output of the first and second sensors 379, 479on the first and second sensor levers 370, 470 is also linear,constantly proportional, predictable, and consistent for bothparallelogram linkages 320, 420.

[0074] The restriction plate 520 provides travel stops for the dualparallelogram linkage 220. The restriction plate 520 has a first endportion 521 and a second end portion 522 opposite the first end portion.A lower surface 531 of the first end portion 521 prevents the first endportion 281 of the housing 280 from moving upward more than apredetermined amount as an upper surface 283 a of the first end portion281 of the housing 280 engages the lower surface 531. A lower surface532 of the second end portion 522 prevents the second end portion 282 ofthe housing 280 from moving upward more than a predetermined amount asan upper surface 293 a of the second end portion 282 of the housing 280engages the upper surface 532. The typical upward amount of travelpermitted by these stops is 1.0 mm.

[0075] Any initial stresses incurred by the first and second sensors379, 479 due to initial bending of the first and/or second sensor levers370, 470 caused by manufacturing tolerances or assembly tolerances(i.e., tightening of the fastener, etc.) may be factored out during aninitial calibration of the first and second sensors. The first andsecond sensor levers 370, 470 essentially bend only in a vertical planeabout a horizontal axis (FIGS. 4-6). As stated earlier, torsional andlateral stresses are decoupled from the bending stresses by the upperand lower curved surfaces 375, 377, 475, 477 of the first end portions372, 472 of the first and second sensor levers 370, 470. Because theseat belt webbing 12 generally imparts upward loads to the dualparallelogram linkage 220, the upper curved surfaces 375, 475 mainlyprovide stability to the first and second sensor levers 370, 470 andensure that the first and second sensor levers 370, 470 return to theirneutral positions (FIG. 3). The intermediate portions 355, 365, 455, 465of the first, second, third, and fourth beams 352, 362, 452, 362, muchthicker than the first and second sensor levers 370, 470, support loadscreated by the seat belt webbing 12 and transmit these loads to thevehicle floor pan 19.

[0076] The first end portions 372, 472 of the first and second sensorlevers 370, 470 may thereby pivot, or rotate, slightly as the first endportions 372, 472 are forced upward by the intermediate portions 365,465 of the second and fourth beams 362, 462. As viewed in FIGS. 4-6, thefirst, second, third, and fourth beams 352, 362, 452, 462 are forcedinto the “S” shapes while the first and second sensor levers 370, 470are bent upward as simple cantilevers.

[0077] The first and second sensors 379, 479 produce output signalsdirectly proportional to the vertical force applied to the seat beltwebbing 12. Overloading of the first and second sensors 379, 479 isprevented by the lower surfaces 531, 532 of the first and second endportions 521, 522 of the restriction plate 520, as discussed above. Thefirst and second sensors 379, 479, while preferably strain gaugesensors, may be any suitable sensors.

[0078] From the above description of the invention, those skilled in theart will perceive improvements, changes and modifications. Suchimprovements, changes and modifications are intended to be includedwithin the scope of the appended claims.

Having described the invention, the following is claimed:
 1. Anapparatus comprising: seat belt webbing for helping to protect anoccupant of a vehicle; a first parallelogram linkage including a firstbeam and a second beam parallel to said first beam, said first andsecond beams each bending in response to at least part of a load appliedby said seat belt webbing; a first sensor lever interposed between saidfirst and second beams, said first sensor lever having a connection withsaid first and second beams, said connection causing said first sensorlever to deflect upon bending of said first and second beams; and afirst sensor for sensing the deflection of said first sensor lever andproviding a first output signal indicative of the amount bending of saidfirst and second beams.
 2. The apparatus as defined in claim 1 whereinsaid first and second beams each have adjacent interconnected first endswhich receive at least part of the load from said seat belt webbing,said first and second beams each further having adjacent interconnectedsecond ends, said second ends transmitting the part of the load to thevehicle.
 3. The apparatus as defined in claim 2 further including afastener assembly for securing said apparatus to the vehicle.
 4. Theapparatus as defined in claim 1 wherein said first sensor receives partof the load applied by said seat belt webbing, the output signal beingcombined with another output signal indicative of another part of theload applied by said seat belt webbing to produce an angle valueindicative of the direction in which the load is applied by said seatbelt webbing.
 5. The apparatus as defined in claim 1 further including asecond parallelogram linkage for sensing another part of the loadapplied by said seat belt webbing.
 6. The apparatus as defined in claim5 wherein said second parallelogram linkage comprises: a third beam anda fourth beam parallel to said third beam, said third and fourth beamseach bending in response to the other part of the load applied by saidseat belt webbing; a second sensor lever interposed between said thirdand fourth beams, said second sensor lever deflecting upon bending ofsaid third and fourth beams; and a second sensor for sensing thedeflection of said second sensor lever and providing a second outputsignal indicative of the amount of bending of said third and fourthbeams, the second output signal being combined with the first outputsignal to produce an angle value indicative of the direction in whichthe load is applied to said apparatus by said seat belt webbing and atension value indicative of the magnitude of the vertical component offorce applied to said apparatus by said seat belt webbing.
 7. Theapparatus as defined in claim 6 wherein said third and fourth beams eachhave adjacent interconnected first ends which receive the other part ofthe load from said seat belt webbing, said third and fourth beams eachfurther having adjacent interconnected second ends, said second endstransmitting the other part of the load to the vehicle.
 8. The apparatusas defined in claim 7 wherein said seconds ends of said first and secondbeams are adjacently interconnected with said second ends of said thirdand fourth beams.
 9. The apparatus as defined in claim 1 wherein saidfirst sensor lever includes a first curved surface engaging a lowersurface of said first beam and a second curved surface engaging an uppersurface of said second beam.
 10. The apparatus as defined in claim 9wherein said first and second curved surfaces allow pivoting of one endportion of said first sensor lever as said first sensor lever isdeflected by at least one of said first and second beams.
 11. Theapparatus as defined in claim 1 further including a plate member with asurface defining a travel stop, said surface limiting movement of saidfirst ends of said first and second beams as said first and second beamsbend.
 12. The apparatus as defined in claim 11 further including ahousing for restricting said first ends of said first and second beamsfrom pivoting relative to said housing.
 13. The apparatus as defined inclaim 1 wherein said first sensor lever has a longitudinal axis, saidfirst beam and said second beam each being disposed equidistantly fromsaid longitudinal axis when said first and second beams are in anunloaded condition.
 14. An apparatus comprising: seat belt webbing forhelping to protect an occupant of a vehicle; and a dual parallelogramlinkage, said dual parallelogram linkage comprising: a first beam and asecond beam parallel to said first beam, said first and second beamseach having adjacent interconnected first ends which receive a firstcomponent of a load from said seat belt webbing, said first and secondbeams each having adjacent interconnected second ends which receive asecond component of the load from said seat belt webbing, said first andsecond beams each further having adjacent interconnected middleportions, said middle portions transmitting the first and secondcomponents of the load to the vehicle, said first and second beams eachbending in response to the load from said seat belt webbing; a sensorlever interposed between said first and second beams, said sensor leverhaving a first connection with said first and second beams, said sensorlever further having a second connection with said first and secondbeams, said first connection causing a first part of said sensor leverto deflect upon bending of said first and second beams, said secondconnection causing a second part of said sensor lever to deflect uponbending of said first and second beams; a first sensor for sensing thedeflection of said first part of said sensor lever and providing a firstoutput signal indicative of the amount bending of said first and secondbeams by the first component of the load; and a second sensor forsensing the deflection of said second part of said sensor lever andproviding a second output signal indicative of the amount bending ofsaid first and second beams by the second component of the load.